Question for you: what do you see on your login screen? Are the graphics OK?
If the graphics are OK up to the login screen, then goes wonky after login, that suggests the problem lies elsewhere.
Try booting to runlevel 3, su to root, then run yast. Use the arrow keys to scroll down to the Hardware category and press enter. Then select the Graphics card and monitor category and press enter. Try to configure the card and driver that way. When all done, run "init 5" and see what happens.